(1) The Field of the Invention comprises heat exchangers for purposes of recycling waste heat, cooling, and ventilating.
(2) Prior Art
So far as is presently known, conventional heat exchangers employ heating tubes developed in the last century by A. M. Perkins which, as described in U.S. Pat. No. 1,872,363 to Thurm, issued Aug. 16, 1932, comprise a straight evacuated tube containing a suitable heat transfer agent and hermetically sealed at both ends. By exposing one end of the tube to heat, the agent is vaporized, the vapors travel to the other cooler end where they are condensed, giving up heat of condensation which may be recovered. The heated end is usually termed the evaporator and the cooled end the condenser; and if the evaporator is lowered below the condenser, the action is improved by having gravity aid the return of the condensate to the evaporator. These Perkins tubes are used in present day commercial heat exchangers, such as those described in U.S. Pat. Nos. 3,788,388 and 3,865,184, which show operation at orientations ranging from the horizontal to positions in which the evaporator is slightly elevated, or tilted, above the condenser, these tilt positions being described as useful to reduce the efficiency of the unit, even to shutting off the same. Obviously, such elevations are adverse to high heat exchanger capacity because they retard or eliminate the above mentioned effect of gravity. The user of these commercial units is instructed that a favorable tilt, i.e., evaporator below the condenser, is necessary to provide adequate capacity, or to operate in winter, and that a tilt control mechanism is required for year round, i.e., both summer and winter, operation, for frost prevention on the weather face of the exhaust side of a unit, and for regulating the temperature of supply air leaving the unit (and entering a building) to avoid over-recovery of heat. Such a mechanism, which is described in said 3,788,388 patent, comprises at least eight structures, not including a number of flexible connections between the unit and the ductwork, and is expensive as well as detractive of the valued passive quality of the heat exchanger and conducive to a degree of long term unreliability.
It is clear, therefore, from the foregoing that operation of a heat exchanger with Perkins tubes at a horizontal orientation will not provide a desired high heat transport (a result confirmed by work described below), that for high heat transport, among other cases, a favorable tilt is required which for automatic operation necessitates use of tilt-producing and tilt control mechanism, and that operation is reduced or even shut off at unfavorable or adverse tilts. This last result raises a separate problem of unavoidable, accidental, and/or initially undetected adverse tilts which may extend up to 0.5 or 1 inch, or more, and which may be and frequently are present owing to the difficulty, especially with tubes of long length, of determining true horizontal and/or of permanently maintaining it; various reasons may account for the difficulty, such as imprecise use of levelling tools by workmen, or the presence of slight undetected damage to the tubes, or the tendency of buildings to shift, and the like. A heat exchanger employing conventional Perkins tubes is unable to operate effectively, or even at all, in the presence of accidentally produced adverse tilts.
The foregoing disadvantages are avoided by the heat exchanger, and elements therefor, described herein which operates at a horizontal orientation and produces high heat transport without need for tilt mechanisms, and which is substantially insensitive to accidentally produced adverse tilts. Among these and other advantages to be described is the provision of an element having a significantly greater driving head, and thus better heat transport, than a Perkins tube.